1. Field of the Invention
The present invention relates to a magnetic sensor capable of detecting a variation of a magnetic field with high sensitivity and further to a current sensor capable of detecting a variation of a current flowing through a conductor with high sensitivity.
2. Description of the Related Art
In measuring correctly a control current which flows through a circuit of control machinery, a method that resistances are connected in series within the circuit to measure a voltage drop of the resistances is applied in general. In this case, however, a load different from the control system is given, and there is a possibility that an adverse influence may be exerted on the control system. Consequently, a method of indirectly measuring a control current by detecting the gradient of a current magnetic field generated by the control current has been used. Specifically, a control current is supplied to a curved, U-shaped conductor, and variation of current magnetic fields produced around the curved conductor is detected by use of a Hall device (for example, refer to Japanese Patent Publication No. H07-123090).
However, the above-described current sensor has problems that a miniaturization is difficult and that the linearity of detection sensitivity relative to varied magnetic fields or high-frequency response are inadequate, etc. For this reason, a current sensor, in which a giant magnetoresistive element developing a Giant Magneto-Resistive effect (hereinafter referred to as GMR element) is arranged in a current magnetic field generated by the control current in order to detect its gradient instead of the Hall element, has been proposed. That current sensor using such GMR elements can improve the detection sensitivity and high-frequency response, and what is more, detection characteristics can be made stabilized against a temperature change.